הלכה על כלאים 1:11

From the laws of the commandment is that which they, may their memory be blessed, said (Moed Katan 2b) that it is one whether one sows or weeds or covers with dirt - they are all included in sowing, to be lashed for them. And whether he covered [the seeds] with his hand, with his foot or even with a tool - he is lashed for all of them. And one who sows them in a holed pot, is like he sows in the actual ground (Mishnah Kilayim 7:8). And that which they said (Talmud Yerushalmi Kilayim 1:1) that there is only a prohibition on account of forbidden mixtures of seeds with seeds that are fitting for human food. But the bitter seeds - even those that are capable of healing people - do not have [the prohibition] of forbidden mixtures of seeds. And behold, forbidden mixtures of trees are included in this negative commandment of "your field shall you not sow [with] a forbidden mixture." However the prohibition of forbidden mixtures of trees is only by way of grafting - for example, that he grafted a sprig of an apple tree to a citron (etrog) tree, and all that is similar to it, that are two species. But by way of sowing - for example, to sow the seed of a tree with [other] seeds - this thing is permissible even from the outset; except for the vineyard, as we will explain in the Order of Ki Tetseh (Sefer HaChinukh 549), with God's help.